Cancer incidence due to excess body weight and leisure-time physical inactivity in Canada: implications for prevention.

OBJECTIVE: This analysis aimed to estimate the number of incident cases of various cancers attributable to excess body weight (overweight, obesity) and leisure-time physical inactivity annually in Canada.
METHODS: The number of attributable cancers was estimated using the population attributable fraction (PAF), risk estimates from recent meta-analyses and population exposure prevalence estimates obtained from the Canadian Community Health Survey (2000). Age-sex-site-specific cancer incidence was obtained from Statistics Canada tables for the most up-to-date year with full national data, 2007. Where the evidence for association has been deemed sufficient, we estimated the number of incident cases of the following cancers attributable to obesity: colon, breast, endometrium, esophagus (adenocarcinomas), gallbladder, pancreas and kidney; and to physical inactivity: colon, breast, endometrium, prostate, lung and/or bronchus, and ovarian.
RESULTS: Overall, estimates of all cancer incidence in 2007 suggest that at least 3.5% (n=5771) and 7.9% (n=12,885) are attributed to excess body weight and physical inactivity respectively. For both risk factors the burden of disease was greater among women than among men.
CONCLUSION: Thousands of incident cases of cancer could be prevented annually in Canada as good evidence exists for effective interventions to reduce these risk factors in the population.